Colombia boss Jose Pekerman admitted his team ran out of steam as they tried to chase down Japan with 10 men in their opening World Cup match on Tuesday.

The South American side had Carlos Sanchez sent off and went 1-0 down from the resulting penalty within the first six minutes of their match in Saransk -- but still managed to equalize and keep the pressure on Japan before eventually losing 2-1.

"After scoring that goal, we lost because we were worn down, we were tired, and even if I tried subbing on some fresh players, it was hard to make a difference," said Pekerman, 68.

The 2014 World Cup quarterfinalists were reduced to 10 men when Sanchez's arm made contact with the ball in the area three minutes into the game. Shinji Kagawa converted the spot kick.

But Colombia counter-punched, stayed positive and created chances, eventually drawing even when Juan Quintero snuck a free kick under the wall and past Eiji Kawashima.

Changing ends at 1-1 showed that Colombia had "survived" the early setback, Pekerman said, but he was fighting a bigger battle against his players' fatigue.

"We had one man less in the middle and in our defense where Japan is strong with Kagawa," Pekerman said.

Not even the introduction of Bayern Munich star James Rodriguez -- who tore Japan apart in a 4-1 group stage defeat four years ago, but has been recovering from an injury in Russia -- could turn the tide.

"If you look at the players that I subbed on, it shows I was not accepting a defensive style of play. The team was supposed to emerge from our half and I wanted them to play along the sides so they could pass the ball forward so we could cause Japan problems."

And that they did. After Yuya Osako scored Japan's second, he was forced to make a desperate late block to stop Rodriguez getting a shot on target from a dangerous position.

But more generally, for long stretches of the game it was not obvious the South Americans were a man down, at least not until the final 20 minutes.

Despite losing their Group H opener, Pekerman said Colombia could take away plenty of positives as they prepare to next face Poland, who lost 2-1 to Senegal later on Tuesday.

"The positive side is that you can see the team managed to rise to the occasion, even after losing one of our most important players," the Argentine said.

"This is a good reaction, if we can do that, it shows we have the ability to move forward in the next matches and even win them. We can make up for this first defeat in the next two matches."